The role of thermo-poro-elastic effects in the interpretation of gravity data

The study of gravity changes induced by magma chambers in volcanic environments has long been used to monitor unrest phases and to estimate the volumes and masses of magma intrusions. However, magma is not the sole driver of the observed deformation and gravity changes. Hydrothermal systems within the volcanic structure can also play a significant role. Recent advances in Thermo-Poro-Elastic (TPE) inclusion models have made it possible to efficiently and accurately simulate the mechanical effects caused by an increase of temperature and pore-pressure of fluids in a reservoir. In this work, we calculate the gravity variations induced by a disk-shaped inclusion. We model gravity variations induced by increments of pore-pressure and temperature within different fluid phases. We also consider the superposition of the effects of a TPE inclusion with a deeper magma chamber. The comparison with the data measured at the Campi Flegrei caldera (Italy) allows us to draw some suggestions on the use and interpretation of these results. Our findings demonstrate that these effects are significant and cannot be overlooked when interpreting gravimetric data during unrest phases and to assess geohazard levels.